feat: Add AndroidKeyMetastate class for keyboard metastate constants #650

Job	Run time
flutter_e2e_test (macos-15, flutter-ios)	12m 43s
flutter_e2e_test (ubuntu-latest, flutter-android)	4m 52s
android_test (test/functional/android/appium_service_tests.py test/functional/android/chrome_test...	4m 8s
ios_test (test/functional/ios/safari_tests.py, func_test_ios1)	9m 48s
	31m 31s

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